Coordinated Access and Backhaul Networks

ABSTRACT

A communications network comprises performance determination circuitry and link control circuitry. The performance determination circuitry is operable to determine performance of a microwave backhaul link between a first microwave backhaul transceiver and a second microwave backhaul transceiver. The microwave backhaul link backhauls traffic of a mobile access link. The link control circuitry is operable to, in response to an indication from the performance determination circuitry that the performance of the microwave backhaul link has degraded, adjust one or more signaling parameters used for the mobile access link. The link control circuitry is operable to, in response to the indication that the performance of the microwave backhaul link has degraded, adjust one or more signaling parameters used for the backhaul link in combination with the adjustment of the parameter(s) of the access link.

PRIORITY CLAIM

This application is a divisional of U.S. patent application Ser. No.14/244,875 filed Apr. 3, 2014 (now U.S. Pat. No. 9,363,689), which alsoclaims priority to the following application(s), each of which is herebyincorporated herein by reference:

U.S. provisional patent application 61/807,829 titled “Adaptive WirelessBackhaul Link” filed on Apr. 3, 2013, now expired; and

U.S. provisional patent application 61/921,608 titled “CoordinatedAccess and Backhaul Networks” filed on Dec. 30, 2013, now expired.

BACKGROUND

Conventional microwave backhaul links suffer from high cost, high powerconsumption, and performance that is highly dependent on environmentalconditions. Limitations and disadvantages of conventional andtraditional approaches will become apparent to one of skill in the art,through comparison of such systems with some aspects of the presentinvention as set forth in the remainder of the present application withreference to the drawings.

BRIEF SUMMARY OF THE INVENTION

Systems and methods are provided for coordinated access and backhaulnetworks, substantially as shown in and/or described in connection withat least one of the figures, as set forth more completely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a diagram illustrating backhaul of an access network linkover a wireless microwave backhaul link.

FIG. 1B depicts an example implementation of the remote radio head ofFIG. 1A.

FIG. 1C depicts an example implementation of the microwave backhaultransceivers of FIG. 1A.

FIG. 1D depicts an example implementation of the baseband unit of FIG.1A.

FIG. 2 depicts waveforms illustrating coordination of access, fronthaul,and backhaul networks.

FIG. 3 is a flowchart illustrating an example process for coordinationof access, fronthaul, and backhaul networks.

FIG. 4 depicts adaptively controlling digitization of an access networksignal based on performance of a microwave link over which the signal isto be backhauled.

FIG. 5A depicts a portion of an example network comprising a pair ofmicrowave backhaul nodes.

FIG. 5B depicts an example implementation of the baseband unit of FIG.5A.

FIG. 5C depicts an example implementation of the microwave backhaultransceivers of FIG. 5A.

FIG. 6A depicts an example implementation of microwave backhaultransceiver operable to support multiple concurrent links.

FIGS. 6B and 6C illustrate adaptation of a number of backhaul linksbetween a pair of microwave backhaul nodes.

FIGS. 7A and 7B illustrate adaptation of backhaul link bandwidth.

FIG. 7C depicts a tradeoff between bandwidth and capacity for an examplebackhaul link.

FIG. 8 illustrates adaptive duty cycling of a microwave backhaul link.

FIGS. 9A and 9B illustrate a microwave backhaul node operable tobackhaul a plurality of integrated transceivers.

DETAILED DESCRIPTION OF THE INVENTION

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory may comprise afirst “circuit” when executing a first one or more lines of code and maycomprise a second “circuit” when executing a second one or more lines ofcode. As utilized herein, “and/or” means any one or more of the items inthe list joined by “and/or”. As an example, “x and/or y” means anyelement of the three-element set {(x), (y), (x, y)}. As another example,“x, y, and/or z” means any element of the seven-element set {(x), (y),(z), (x, y), (x, z), (y, z), (x, y, z)}. As utilized herein, the term“exemplary” means serving as a non-limiting example, instance, orillustration. As utilized herein, the terms “e.g.,” and “for example”set off lists of one or more non-limiting examples, instances, orillustrations. As utilized herein, circuitry is “operable” to perform afunction whenever the circuitry comprises the necessary hardware andcode (if any is necessary) to perform the function, regardless ofwhether performance of the function is disabled, or not enabled, by someuser-configurable setting. As used herein, “microwave” frequencies rangefrom approximately 300 MHz to 300 GHz and “millimeter wave” frequenciesrange from approximately 30 GHz to 300 GHz. Thus, the “microwave” bandincludes the “millimeter wave” band.

In accordance with aspects of this disclosure, data from an accessnetwork may be communicated (“backhauled”) over a wireless microwavelink. Conventionally, signaling parameters (e.g., transmit power,receive sensitivity, sample rate, sample resolution, symbol rate,modulation type, modulation order, FEC type, FEC code rate, interleaverdepth, and/or the like) of the access network communications beingbackhauled over the wireless microwave backhaul link are configuredwithout regard to conditions on the microwave link and are configured toperform reliably in particular “corner cases” (i.e., extremes forvarious conditions) set forth in the applicable standards (e.g.,cellular, WiMax, Wi-Fi, and/or other access network standards). Suchcorner cases for the access network communications may correspond todifferent conditions than the corner cases for the wireless microwavebackhaul link. For example, a corner case for a wireless microwavebackhaul link may correspond to conditions of high atmosphericattenuation (e.g., heavy rain, snow, smog, fog, etc.) whereas an accessnetwork link may be relatively impervious to atmospheric conditions dueto communications of the access network being at much lower frequencies.Accordingly, aspects of this disclosure take advantage of the fact that,in conditions where the microwave backhaul link has little or no linkmargin, the access network may still have link margin (or vice versa).In such instances, signaling parameters used for the microwave backhaullink may be adjusted to reduce the data rate of the microwave backhaullink (e.g., by lowering sampling resolution, lowering sampling rate,decreasing FEC code rate, and/or the like) in reliance on the fact thatthe excess link margin in the access network link is great enough thatthe overall link margin (e.g., between the access terminal and thebaseband unit) is sufficient to achieve performance requirements. Inother words, the system may perform coordinated configuration of theaccess network link and the microwave backhaul link to maintain overalllink margin (comprised of margin of the access network link plus marginof the backhaul link) within determined limits A lower limit of theoverall link margin may, for example, be determined based on minimumrequired throughput, latency, and/or the like. An upper limit of theoverall link margin may, for example, be determined based on powerconsumption targets.

FIG. 1A is a diagram illustrating backhaul of an access network linkover a wireless microwave backhaul link. Shown are a tower 108 to whichaccess network antennas 112 and remote radio head (RRH) 110 areattached, a baseband unit 104, a tower 112 a to which microwave backhaulnode 120 a (comprising transceiver 114 a and antenna 116 a) is attached,and a tower 112 b to which microwave backhaul node 120 b (comprisingtransceiver 114 b and antenna 116 b) is attached. Also shown is anaccess network terminal 107.

The access network terminal 107 may be, for example, a smartphone,laptop, tablet computer, set-top-box, and/or the like. The accessnetwork terminal 107 is configured for communicating over link 105between it and the antennas 112. The access network (to which link 105belongs) may be, for example, a mobile access network or a wired oroptical access network. Examples of a mobile access network includecellular (e.g., 4G LTE), Wi-Max, and Wi-Fi. Examples of a wired oroptical access network include data over cable service interfacedspecification (DOCSIS), digital subscriber line (DSL), and/or the like.

The antennas 112 are configured for radiating and capturing signals ofthe access network. The captured signals are conveyed to the RRH 110 andthe radiated signals are received from the RRH 110.

Uplink Traffic

For uplink traffic from the terminal 107 to the core network 102, theterminal 107 transmits a signal onto link 105. The signal on the link105 is captured by an antenna 112 and conveyed to the RRH 110. The RRH110 processes (e.g., amplifies, downconverts, filters, and/or the like)the signals received from the antennas 112 and transmits the resultingaccess network signal to the microwave backhaul transceiver 114 a vialink 113 a (which is shown as a wired or optical fiber link, but whichmay also be or include a wireless link).

The microwave backhaul transceiver 114 a processes, as necessary (e.g.,packetizes, encodes, modulates, upconverts, beamforms, amplifies, and/orthe like) the access network signal received from the RRH 110 fortransmitting the access network signal over the microwave backhaul link118. In an example implementation, the access network signal output bythe RRH 110 may be an analog signal (i.e., the RRH 110 performsanalog-domain processing up to, but not including, analog-to-digitalconversion) which the microwave transceiver may digitize prior tosending over the backhaul link. The digitization of the access networksignal from the RRH 110 may, for example, be in accordance with thecommon public radio interface (CPRI) standard. That is, the microwavebackhaul transceiver 114 a may perform transmit-side CPRI processing ofthe access network signal. In another example implementation, thedigitization (e.g., transmit-side CPRI processing) of the access networksignal may be performed in the RRH 110 prior to sending it to themicrowave backhaul transceiver 114.

The microwave transceiver 114 b receives the microwave signal overmicrowave backhaul link 118, processes the signal as necessary (e.g.,downconverts, filters, beamforms, and/or the like) for conveyance to theBBU 104 via link 113 b (shown as wired or optical fiber but which may bewireless). The processing may recover the access network signal outputby the RRH 110. In this manner, the existence of the microwave backhaullink 118 between the RRH 110 and the BBU 104 may be transparent to theRRH 110 and BBU 104. In an example implementation, processing of thereceived signal by the microwave transceiver 114 b may includereceive-side CPRI processing.

The BBU 104 receives the signal via link 113 and demodulates the accessnetwork signal to recover data which is then conveyed to the corenetwork 102 via link 103 (which is shown as a wired or optical fiberlink, but which may also be or include a wireless link).

Downlink Traffic

For downlink traffic, the BBU 104 receives data from the core network102 via the link 103. The BBU 104 then modulates the data onto a signalin accordance with the access network standard/protocols in use,resulting in an access network signal. In an example implementation, theaccess network signal is output onto link 113 b.

The microwave backhaul transceiver 114 b processes, as necessary (e.g.,packetizes, encodes, modulates, upconverts, beamforms, amplifies, and/orthe like) the access network signal received from the BBU 104 fortransmitting the signal over the microwave backhaul link 118. In anexample implementation, the access network signal is an analog signal(i.e., the BBU 104 converts the signal to analog and outputs it the sameas if outputting the signal directly to the RRH 110). In such animplementation, the microwave transceiver 114 b may digitize the signalprior to sending it over the backhaul link. The digitization of theaccess network signal may, for example, be in accordance with the commonpublic radio interface (CPRI) standard. That is, the microwave backhaultransceiver 114 b may perform transmit-side CPRI processing of theaccess network signal. In another example implementation, thedigitization (e.g., transmit-side CPRI processing) may be performed inthe BBU 104 prior to the access network signal being sent over the link113 b.

The microwave transceiver 114 a receives the microwave signal overmicrowave backhaul link 118, processes the signal as necessary (e.g.,downconverts, filters, beamforms, and/or the like) for conveyance to theRRH 110 via link 113 a. The processing may recover the access networksignal output by the BBU 104. In this manner, the existence of themicrowave backhaul link 118 between the RRH 110 and the BBU 104 may betransparent to the RRH 110 and BBU 104. In an example implementation,processing of the received signal by the microwave transceiver 114 a mayinclude receive-side CPRI processing.

The RRH 110 receives the access network signal via the link 113 a,processes it as necessary (e.g., upconverts and amplifies it) fortransmission onto the access network link 105.

FIG. 1B depicts an example implementation of the remote radio head ofFIG. 1A. The example RRH 110 comprises an access network front-endcircuit 142 that converts between RF access network signals on antennas112 and baseband access network signals on link 113 a. Various signalingparameters used by the circuit 142 may be controlled based on controldata 134 which may originate from the microwave transceiver(s) 114 aand/or 114 b and which may be conveyed to the RRH 110 via the link 113a. The control data may be communicated in-band with the access networksignal on link 113 or out-of-band with the access network signal (e.g.,at different times, on different frequency, etc.).

FIG. 1C depicts an example implementation of the microwave backhaultransceivers of FIG. 1A. The example microwave backhaul transceiver 114_(X) (which is representative transceivers 114 a and 114 b) comprisesinterface circuit 122, modulator/demodulator (Mod/demod) circuit 124,microwave radio front-end 126, performance determination circuit 130,and link control/coordination circuit 132.

The interface circuit 122 is operable to interface the link 113 _(X)(which is representative of links 113 a and 113 b) and themodulator/demodulator circuit 124. For an incoming access network signalfrom the link 113 _(X), interface circuit 122 processes the accessnetwork signal to make it suitable for the circuit 124 to process it(e.g., encode, map, interleave, and/or the like) for transmission ontothe microwave backhaul link. For example, the interface 122 may performtransmit-side CPRI functions. For an incoming microwave backhaul signalfrom the link 118, interface circuit 122 processes the demodulatedsignal from the circuit 124 to make it suitable for transmission ontothe link 113 _(X). For example, the interface 122 may performreceive-size CPRI functions. Various parameters used by the interfacecircuit 122 (e.g., sampling rate and/or sampling resolution) may becontrolled based on control data 134 which may originate from the linkcontrol/coordination circuit 132 and which may be based on theperformance of the microwave backhaul link determined by the circuit130.

The modulator/demodulator circuit 124 is operable to perform modulationand demodulation functions (e.g., encoding, decoding, symbol mapping,symbol demapping, interleaving, deinterleaving, and/or the like) inaccordance with whatever standards and/or protocols are in use on themicrowave backhaul link(s) 118. In an example implementation, themodulation type (e.g., QAM, PSK, FSK, etc.), order, FEC encoding type(e.g., Reed-Solomon, LDPC, etc.), FEC code rate, interleaver depth,and/or other parameters of the modulator/demodulator circuit 124 may becontrolled via a control signal 134 output by link control circuit 130.In an example implementation, various components of themodulator/demodulator circuit 124 may be enabled and disabled via thecontrol signal 134.

The microwave radio front-end 126 is operable to perform data conversion(e.g., analog-to-digital (ADC) and digital-to-analog (DAC)) andanalog-domain signal processing functions (e.g., filtering,upconversion, downconversion, and amplification) for interfacing toantenna 116. In an example implementation, filter frequencies, localoscillator frequencies, gain settings (e.g., of a power amplifier offront-end 126), ADC resolution, DAC resolution, and/or other parametersof the front-end circuit 126 may be controlled via the control signal134 output by link control circuit 132.

The performance determination circuit 130 is operable to determine oneor more performance metrics of the microwave backhaul link 118 and/ordetermine environmental conditions (e.g., temperature, twist and swaydue to wind, atmospheric attenuation, and/or the like), which may impactperformance of the microwave link 118. The performance determinationcircuit 130 may be operable to determine the performance metrics and/orenvironmental conditions continually, periodically, and/or occasionally(e.g., in response to occurrence of determined events). Exampleperformance metrics the performance determination circuit 130 maydetermine include signal-to-noise ratio (SNR), bit error rate (BER),packet error rate (PER), and/or symbol error rate (SER).

In an example implementation, the performance determination circuit 130may be operable to determine atmospheric attenuation based on one ormore measured performance metrics for the microwave backhaul link 118.In an example implementation, the performance determination circuit 130may be operable to determine atmospheric attenuation and/or otherenvironmental conditions based on data communicated with a network(e.g., data from a weather service which the performance determinationcircuit 130 may access via the interface 122 and the Internet). In anexample implementation, the performance determination circuit 130 maycomprise sensors and/or instrumentation for measuring atmosphericconditions and/or directly measuring atmospheric attenuation. Suchinstrumentation/sensors may comprise, for example, a hygrometer, apsychrometer, and/or a radiometer. In an example implementation, theperformance determination circuit 130 may be able to predict futureatmospheric attenuation (e.g., based on current and/or past measuredatmospheric attenuation) and/or other environmental conditions andschedule configuration of parameters used by the circuit(s) 122, 124,126, 142, and/or 120 in advance.

The link control circuit 132 is operable to jointly control signalingparameters used for the microwave backhaul link 118 and access networklink 105 based on the current and/or predicted performance determined bythe circuit 130. In this manner, overall link margin across themicrowave backhaul link 118 and access network link 116 may be managedto achieve optimal combinations of capacity, latency, power savings,and/or other performance criteria. Furthermore, rather than themicrowave backhaul link always being configured for worst-caseconditions as is conventionally the case, the microwave transceivers 114a and 114 b can burn more power to handle worst-case conditions whichoccur, for example, 0.0001% of the time, but also offer higherperformance (e.g., higher reliability, higher throughput, lower latency,lower power consumption, and/or the like) the remaining 99.999% of thetime.

FIG. 1D depicts an example implementation of the baseband unit of FIG.1A. The example BBU 104 comprises modulator/demodulator 128 and anetwork interface circuit 129. The modulator/demodulator 128 is operableto perform modulation and demodulation functions (e.g., encoding,decoding, symbol mapping, symbol demapping, interleaving,deinterleaving, and/or the like) in accordance with whatever standardsare in use in the access network. The network interface circuit 122 isoperable to send and receive signals in accordance with whateverstandards or protocols are in use on the link 103 (e.g., Ethernet).

FIG. 2 depicts waveforms illustrating coordination of access, fronthaul,and backhaul networks.

At time T1, signal to noise ratio (SNR) of the microwave backhaul link118 degrades (e.g., as a result of increased atmospheric attenuation, orsome other condition that impacts the microwave frequencies on which thelink 118 operates) from a level 212 that is above the threshold SNR to alevel 210 that is below the threshold SNR. In response to thisdegradation in performance of the microwave backhaul link 118, asindicated by arrow 202, one or more signaling parameters (e.g., transmitpower, modulation order, sampling resolution, FEC code rate, etc.) usedfor the access link 105 are adjusted to increase the SNR of the accesslink 105, and one or more signaling parameters (e.g., transmit power,modulation order, sampling resolution, FEC code rate, etc.) of thebackhaul link 118 are adjusted to decrease the threshold SNR of themicrowave backhaul link from a level 211 to a level 209. Thiscombination of adjustments to the signaling parameters of the accesslink 105 and the backhaul link 118 result in the overall link marginover the two links in series being maintained within desired limits.This may be possible because atmospheric attenuation, for example, mayhave a relatively large impact on microwave frequencies used for thebackhaul link 118 but relatively little impact on frequencies used forthe access link 105. Accordingly, from time T1+Δ to T2+Δ, one or moresignaling parameters used for the access link 105 may be set to takeadvantage of favorable signal conditions on the access link 105 tocompensate for the unfavorable signal conditions on the backhaul link118.

At time T2, SNR of the microwave backhaul link 118 improves from thelevel 210 to the level 212. In response, as indicated by arrow 204, thesignaling parameters of access network link 105 may revert to valuescorresponding to SNR level of 222 (e.g., resulting in further powersavings in the access network), and the signaling parameters of thebackhaul link 118 may revert to values corresponding to the SNRthreshold of 211.

At time T3 SNR of the microwave backhaul link 118 improves from thelevel 212 to the level 214. In response, as indicated by arrow 206, thesignaling parameters of access network link 105 may be changed to valuescorresponding to SNR level of 220 (e.g., resulting in further powersavings in the access network).

Similarly, although not shown, the cause and response may apply in theother direction. That is, changes in the access link 105 may triggeradaptation of signaling parameters used for the backhaul link 118. Forexample, where the SNR of the access link 105 is low, signalingparameters used for the backhaul link 118 may be configured to increaselink margin of the backhaul link 118 such that overall link margin(e.g., from terminal 107 to BBU 104) is maintained above a determinedminimum threshold.

Although the above describes trading off power consumption vs. linkmargin of the access link 105 and backhaul link 118, the same can beapplied to coordination among any two more of links 105, 113 a, 118, and113 b. For example, signaling parameters used for the links 113 a and/or113 b may be adjusted to reduce power consumption in instances that lesslink margin on the links 113 a and 113 b can be tolerated due tosufficient link margin on the link(s) 105 and/or 118.

FIG. 3 is a flowchart illustrating an example process for coordinationof access, fronthaul, and backhaul networks. In block 302, thecomponents of the network are powered up and the links 118, 113 a, and113 b are established. In block 304, access link 105 is establishedbetween terminal 107 to the RRH 110. In block 306, a condition, such asrain or fog, arises that significantly degrades performance of themicrowave backhaul link 118 but has relatively little impact on theaccess link 105. In block 308, signaling parameters used for the accesslink 105 and/or signaling parameters used for the microwave backhaullink 118 are adjusted to compensate for the degraded performance of thebackhaul link. For example, signaling parameters of the access link 105may be adjusted to increase the SNR on the access link 105 while thenumber of bits per sample and the code rate (i.e., ratio of data bits todata bits +redundant bits) used for transmitting data over the microwavebackhaul link 118 may each be decreased. As another example, where theSNR of the access link 105 is sufficiently high when the backhaul link118 experiences a degradation in performance, the signaling parametersof the access link 105 may be adjusted to reduce the load on thebackhaul link 118. For example, in response to degradation of thebackhaul link 118, the number of bits per sample used on the access link105 may be decreased. This may decrease the SNR on the access link (as aresult of increased quantization noise) as a tradeoff for reducing thebit rate to a level that can be supported by the current conditions onthe backhaul link 118. In this manner, performance may degradegracefully rather than catastrophically.

Shown in FIG. 4 is an example access network signal 402 received fromRRH 110 and being digitized by circuit 122 for communication over themicrowave backhaul link 118. The left axis 406 shows a larger number ofquantization levels (corresponding to a higher number of bits persample) used for quantizing the access network signal 402 whenconditions are good for the microwave link (e.g., clear skies). Theright axis 404 shows a smaller number of quantization levels(corresponding to a lower number of bits per sample) used for digitizingthe access network signal 402 signal when conditions are poor on themicrowave link (e.g., rain or fog). By controlling the number of bitsper sample of the backhaul link in response to increased atmosphericattenuation and/or other conditions negatively impacting the link 118,the user experience (e.g., voice quality of a voice call in progress bythe terminal 107) may be allowed to degrade continually rather thancompletely failing upon signal conditions falling below a threshold.

In accordance with an example implementation of this disclosure, acommunications network comprises performance determination circuitry(e.g., 130) and link control circuitry (e.g., 132). The performancedetermination circuitry may be operable to determine performance of amicrowave backhaul link (e.g., 118) between a first microwave backhaultransceiver (e.g., 114 a) and a second microwave backhaul transceiver(e.g., 114 b). The microwave backhaul link backhauls traffic of a mobileaccess link (e.g., link 105 of a cellular access network). The linkcontrol circuitry may be operable to, in response to an indication fromthe performance determination circuitry that the performance of themicrowave backhaul link has degraded, adjust one or more signalingparameters used for the mobile access link (e.g., to increase SNR of theaccess link). The link control circuitry may be operable to, in responseto an indication from the performance determination circuitry that theperformance of the microwave backhaul link has improved, adjust the oneor more parameters used for the mobile access link (e.g., to decreaseSNR of the access link, allowing for reduced power consumption in theaccess network).

The determination of the performance may comprise a determination ofatmospheric attenuation impacting the microwave backhaul link. Theperformance determination circuitry may be operable to determine theatmospheric attenuation based on data received from a weather serviceaccessible via the communications network. The performance determinationcircuitry may be operable to determine the atmospheric attenuation basedon direct measurement of the atmospheric attenuation by the circuitry ofthe communications network (e.g., via an integrated hygrometer,psychrometer, radiometer, and/or the like). The determination of theperformance may comprise a determination of signal-to-noise ratio of themicrowave backhaul link. The signaling parameters used for the mobileaccess link may comprise one or more of: power transmitted by a remoteradio head (e.g., 110) that handles the mobile access link, order and/ortype of modulation used for the mobile access link, and type and/or coderate of forward error correction used for the mobile access link.

The system may comprise interface circuitry (e.g., 122) and microwavebackhaul transceiver circuitry (e.g., 114 _(X)). The interface circuitrymay be operable to receive an analog mobile access link signal from theremote radio head. The interface circuitry may be operable to sample themobile access link signal to generate a digitized mobile access linksignal. The microwave backhaul transceiver circuitry may be operable tosend the digitized mobile access link signal over the microwave backhaullink. The microwave backhaul transceiver circuitry may operable toreceive the digitized mobile access link signal over the microwavebackhaul link. The microwave backhaul transceiver circuitry may operableto convert the digitized mobile access link signal back to the analogmobile access link signal. The microwave backhaul transceiver circuitrymay operable to convey the analog mobile access signal to a basebandunit, wherein the baseband unit is operable to demodulate the mobileaccess link signal. A sampling resolution and/or sampling rate used bythe interface circuitry may be decreased in response to the indicationfrom the performance determination circuitry that the performance of themicrowave backhaul link has degraded. A sampling resolution and/orsampling rate used by the interface circuitry may be increased inresponse to the indication from the performance determination circuitrythat the performance of the microwave backhaul link has improved.

FIGS. 5A-9B illustrate additional aspects of this disclosure.

FIG. 5A is a diagram illustrating a portion of an example networkcomprising a pair of microwave backhaul nodes. Shown are a tower 508 towhich access network antennas 512 and remote radio head (RRH) 510 areattached, a baseband unit 504, a tower 526A to which microwave backhaulnode 520 a (comprising transceiver 514 a and reflector 516 a) isattached, and a tower 526B to which microwave backhaul node 520 b(comprising transceiver 514 b and antenna 516 b) is attached. At anyparticular time, there may be one or more active (i.e., carrying trafficor synchronized and ready to carry traffic after a link setup time thatis below a determined threshold) links 506 (shown as wireless, but maybe wired or optical) between the RRH 510 and the BBU 504. At anyparticular time, there may be one or more active backhaul links 518between the pair of backhaul nodes 520 a and 520 b.

The antennas 512 are configured for radiating and capturing signals ofan access network (e.g., 3G, 4G LTE, etc. signals to/from mobilehandsets). Although the example pair of microwave nodes 520 a and 520 bare used for backhauling cellular traffic, this is just one example typeof traffic which may be backhauled by microwave nodes, such as 520 a and520 b, that implement aspects of this disclosure. Other example traffictypes are described below with respect to FIGS. 9A and 9B.

For an uplink from a mobile handset to the core network 502, theantennas 512 receive signals from the handset and convey them to the RRH510. The RRH 510 processes (e.g., amplifies, downconverts, digitizes,filters, and/or the like) the signals received from the antennas 512 andtransmits the resulting signals (e.g., downconverted I/Q signals) to thebaseband unit (BBU) 504 via link(s) 506. The BBU 504 processes, asnecessary, (e.g., demodulates, packetizes, modulates, and/or the like)the signals received via link(s) 506 for conveyance to the microwavebackhaul transceiver 514 a via link 117A (shown as wired or optical, butmay be wireless). The backhaul transceiver 514 a processes, as necessary(e.g., upconverts, filters, beamforms, and/or the like), the signalsfrom BBU 504 for transmission via the reflector 516 a over microwavebackhaul link(s) 518. The microwave transceiver 514 b receives themicrowave signals over microwave backhaul link(s) 518, processes thesignals as necessary (e.g., downconverts, filters, beamforms, and/or thelike) for conveyance to the cellular service provider core network 502via link 117B.

For a downlink from the core network 502 to the mobile handset, datafrom the core network is conveyed to microwave backhaul transceiver 514b via link 117B. The transceiver 514 b processes, as necessary (e.g.,upconverts, filters, beamforms, and/or the like), the signals from thecore network 502 for transmission via the reflector 516 b over link(s)518. Microwave transceiver 514 a receives the microwave signals via themicrowave backhaul link(s) 518, and processes the signals as necessary(e.g., downconverts, filters, beamforms, and/or the like) for conveyanceto the BBU 504 via link 117A. The BBU 504 processes the signal fromtransceiver 514 a as necessary (e.g., demodulates, packetizes,modulates, and/or the like) for conveyance to RRH 510 via link(s) 506.The RRH 510 processes, as necessary (e.g., upconverts, filters,amplifies, and/or the like), signals received via link 506 fortransmission via an antenna 512.

FIG. 5B depicts an example implementation of the baseband unit of FIG.5A. The example BBU 504 comprises modulator/demodulator 128 andinterface circuit 522. The modulator/demodulator 128 is operable toperform modulation and demodulation functions (e.g., encoding, decoding,symbol mapping, symbol demapping, interleaving, deinterleaving, and/orthe like) in accordance with whatever cellular standards are in use inthe access network. The interface circuit 522 is operable to send andreceive signals in accordance with whatever standards or agreed-uponprotocols are in use on the link 513 (which may correspond to 117Aand/or 117B of FIG. 5A).

FIG. 5C depicts an example implementation of the microwave backhaultransceivers of FIG. 5A. The example microwave backhaul transceivercomprises interface circuit 522, modulator/demodulator 524, radiofront-end 526, conditions determination circuit 530, and link controlcircuit 532.

The interface circuit 522 is operable to send and receive signals inaccordance with whatever standards or agreed-upon protocols are in useon the link 513 (which may correspond to 117A and/or 117B of FIG. 5A).

The modulator/demodulator 524 is operable to perform modulation anddemodulation functions (e.g., encoding, decoding, symbol mapping, symboldemapping, interleaving, deinterleaving, and/or the like) in accordancewith whatever standards and/or agreed-upon protocols in use on themicrowave backhaul link(s) 518. In an example implementation, themodulation type (e.g., QAM, PSK, FSK, etc.), order, FEC encoding type(e.g., Reed-Solomon, LDPC, etc.), FEC code rate, interleaver depth,and/or other parameters of the circuit 524 may be controlled via acontrol signal 534 output by link control circuit 530. In an exampleimplementation, various components of the circuit 524 may be enabled anddisabled via the control signal 534.

The radio front-end 526 is operable to perform data conversion (e.g.,analog-to-digital (ADC) and digital-to-analog (DAC)) and analog-domainsignal processing functions (e.g., filtering, upconversion,downconversion, and amplification) for interfacing to reflector 516. Inan example implementation, filter frequencies, local oscillatorfrequencies, gain settings (e.g., of a power amplifier of front-end526), ADC resolution, DAC resolution, and/or other parameters of thecircuit 526 may be controlled via the control signal 534 output by linkcontrol circuit 532. In an example implementation, various components ofthe circuit 526 may be enabled and disabled via the control signal 534.For example, the circuit 526 may comprise multiple transmit and receivepaths each of which may be individually controlled (e.g., as describedbelow with reference to FIGS. 6A-6C.

The conditions determination circuit 530 is operable to determineatmospheric attenuation (due to gases and/or aerosols in the atmosphere)experienced by the microwave backhaul link(s) 518. The circuit 530 maydetermine the atmospheric attenuation continually, periodically, and/oroccasionally (e.g., in response to occurrence of determined events). Inan example implementation, the atmospheric attenuation may be determinedbased on measurement/characterization (e.g., in the form of one or moremetrics such as signal-to-noise ratio (SNR), bit error rate (BER),packet error rate (PER), throughput, number of retransmissions, and/orthe like) of data signals communicated over the link(s) 518. In anexample implementation, the atmospheric attenuation may be determinedbased on measurement/characterization of test/calibration signals sendover the link(s) 518. In an example implementation, the atmosphericattenuation may be determined based on data communicated with a network(e.g., data from a weather service which the conditions determinationcircuit 530 may access via the interface 522). In an exampleimplementation, the circuit 530 may comprise sensors and/orinstrumentation for measuring atmospheric conditions and/or directlymeasuring atmospheric attenuation. Such instrumentation/sensors maycomprise, for example, a hygrometer, a psychrometer, and/or aradiometer. In an example implementation, the circuit 530 may be able topredict future atmospheric (e.g., based on current and/or past measuredatmospheric attenuation) and schedule parameter configurationsaccordingly.

The link control circuit 532 is operable to control parameters of themicrowave backhaul link(s) 518 based on the current and/or predictedatmospheric attenuation determined by the circuit 530. In this manner,rather than the microwave backhaul link always being configured forworst-case conditions, the link(s) 518 can handle worst-case conditionsduring the 0.0001% (e.g.,) of the time when they occur, but can offerhigher performance (e.g., higher reliability, higher throughput, lowerlatency, and/or the like) the rest of the time.

In another example implementation, the parameters may comprise number ofconcurrently-active links 518. An example of this is described belowwith reference to FIGS. 6A-6C.

In an example implementation, the parameters may comprise bandwidth ofthe microwave backhaul link(s) 518. An example of this is describedbelow with reference to FIGS. 7A-7C.

In another example implementation, the parameters may comprise dutycycle of the microwave backhaul link(s) 518. An example of this isdescribed below with reference to FIG. 8.

FIG. 6A depicts an example implementation of microwave backhaultransceiver operable to support multiple concurrent links. The examplecircuit 526 in FIG. 6A comprises two Tx/Rx front ends 206A and 206Bwhich may enable two concurrent backhaul links (labeled 518 a and 518b). In an example implementation, the first front-end 206A may be usedfor communicating at a first microwave frequency (e.g., 70 to 95 GHz)and the second front-end 206B may be used communicating at a second,lower frequency that is less susceptible to rain fade or otherconditions that may negatively impact communications on the firstfrequency. For example, the second radio may also be a microwave radiobut may communicate at lower frequency such as 30 to 50 GHz. As anotherexample, the second radio may communicate at cellular frequencies.

In an example implementation, a primary, high-bandwidthhigh(er)-frequency backhaul link 518 a (e.g., 5 GHz wide at 70 GHzand/or 5 GHz at 80 GHz) may provide very high reliability and throughputin clear weather conditions, but reliability and throughput may degraderapidly with rain, fog, etc. Accordingly, a second link 518 b betweenhat may be less susceptible to weather conditions (e.g., because it isat a lower frequency) may be used to improve throughput/reliability ofcommunications between the two towers in poor weather conditions (and/orat other times where the throughput/reliability of the primary link isdegraded). The second link (e.g., at a lower frequency less susceptibleto atmospheric attenuation) may be enabled and disabled based on currentand/or predicted atmospheric attenuation. In an example implementation,while performance of the primary link is degraded, the secondary link518 b may be used for transmitting high priority traffic (e.g., frameheaders, FEC syndrome, most significant bits of data words, and/or thelike) while the remaining traffic is provided best-effort service on theprimary link 518 a. Data transmitted over the secondary link may be usedfor recovering (e.g., error detecting and correcting) data received overthe primary link.

As shown in FIGS. 6B and 6C, when conditions are favorable for the firstlink 518 a (e.g., clear skies), the backhaul nodes 520 a and 520 b maycommunicate via only the first link, but when conditions are such thatperformance of the first link is degraded below a threshold (e.g., rainresulting in atmospheric attenuation rising above a threshold, SNR ofthe link 518 a falling below a threshold, BER of the link 518 a risingabove a threshold, and/or the like) then the second link 518 b may beenabled and used for communicating high-priority traffic.

In an example implementation, the microwave backhaul nodes 520 a and 520b may be operable to trade off bandwidth of the link(s) 518 on one handwith range and/or reliability of the link(s) 518 on the other hand. Forexample, while the link(s) 518 are active, the bandwidth may adapt alongwith changes in the atmospheric attenuation. For example, as atmosphericattenuation increases (e.g., as rain or snow gets heavier) the bandwidthof the link(s) 518 may increase in order to achieve longer range and/orhigher reliability at the expense of decreased spectral efficiency.Conversely, as atmospheric attenuation decreases (e.g., as rain or snowgets lighter) the bandwidth of the link(s) 518 may be decreased (andspectral efficiency increased).

It can be shown that capacity =BW*Log2(1+SNR). Thus, for a low ornegative (in dB) SNR link 518, there may be an optimal capacity aroundan SNR of −5 dB to −10 dB, for example. Accordingly, where there isexcess bandwidth available, the transceivers 514 a and 514 b may beconfigured to sacrifice some of the bandwidth (e.g., by increasing FECcode length) in order to increase capacity. Such adjustment of linkparameters to sacrifice BW in exchange for increased capacity may bedynamically enabled as needed (e.g., during heavy rain or fog). Inaddition to increasing redundancy or FEC code length, another way inwhich the transceivers 514 a and 514 b may be configurable to adjust BWto optimize capacity is to use spread-spectrum techniques. Accordingly,in an example implementation, the use of spread spectrum techniques bythe transceivers 514 a and 514 b for the microwave backhaul links 518may be dynamically enabled as needed (e.g., when atmospheric absorptionis high due to heavy rain or fog).

Referring to FIGS. 7B and 7B, there is shown a link between twomicrowave units which in good signal conditions (FIG. 7A) uses a firstbandwidth, BW1, and in poor signal conditions (FIG. 7B) uses a secondbandwidth, BW2, which is greater than BW1.

FIG. 8 illustrates adaptive duty cycling of a microwave backhaul link.In an example implementation, one or more microwave backhaul links 518may be duty cycled between a first state and a second state. In anexample implementation, the first state is an active state and thesecond state is an inactive state. In such an implementation, circuitryof the transceivers 514 a and 514 b may be powered down while in thesecond state, resulting in reduced power consumption. In otherimplementations, circuitry of transceivers 514 a and 514 b may be cycledamong more than two states. For example, the circuitry may be dutycycled between three states: (1) active; (2) ready to become activeafter a setup time of X seconds or less; (3) ready to become active onlyafter longer than X seconds of setup.

An example of a two-state duty cycle is shown in FIG. 8. Specifically,example duty cycles are shown for three types of conditionscorresponding to three levels of atmospheric attenuation for themicrowave backhaul link 518. In FIG. 8, 802 ₁<802 ₂<802 ₃. Whenatmospheric attenuation is low (e.g., clear skies, low smog, etc.), thusenabling high throughput, the link is active for time 802 ₁ and inactivefor time 802 ₄ minus 802 ₁. When atmospheric attenuation is moderate(e.g., light rain or smog), thus enabling moderate throughput, the linkis active for time 802 ₁ and inactive for time 802 ₄ minus 802 ₂. Whenatmospheric attenuation is high (e.g., heavy rain or fog), enabling onlylow throughput, the link is active for time 802 ₄ (i.e., always active).In the example of FIG. 8, for each duty cycle, the same amount of datais communicated over the link 518 during an amount of time 802 ₄.Different among the three duty cycles is the amount of power consumed indelivering that data and perhaps latency of the data. Thus, in responseto increases in atmospheric attenuation (which corresponds to movingfrom left to right in FIG. 8), the link control circuits 532 of thetransceivers 514 a and 514 b may increase the duty cycle of circuitry ofthe transceiver 514 a and 514 b. Conversely, in response to decreases inatmospheric attenuation (which corresponds to moving from right to leftin FIG. 8), the link control circuits 532 of the transceivers 514 a and514 b may decrease the duty cycle of circuitry of the transceiver 514 aand 514 b.

FIGS. 9A and 9B illustrate a microwave backhaul node operable tobackhaul traffic of a plurality of integrated transceivers. Shown is amicrowave backhaul node 520 similar to the ones discussed above, butadditionally comprising antennas 902 ₁ and 902 ₂, additionally beingconnected to cable 904, and additionally comprising a subassembly 906that additionally comprises a Wi-Fi transceiver 910 a, a cellulartransceiver 910 b, a cable transceiver 910 c, andmultiplexing/demultiplexing circuit 912.

The Wi-Fi transceiver 910 a comprises circuitry operable to transmit andreceive Wi-Fi signals via the antenna 902 ₁. Data to be transmitted maybe received via the backhaul link(s) 518, the transceiver 514, and themux/demux 912. Received data may be output onto the link(s) 518 via themux/demux 912 and transceiver 514.

The cellular transceiver 910 b comprises circuitry operable to transmitand receive cellular (e.g., LTE) signals via the antenna 902 ₂. Data tobe transmitted may be received via the backhaul link(s) 518, thetransceiver 514, and the mux/demux 912. Received data may be output ontothe link(s) 518 via the mux/demux 912 and transceiver 514.

The cable transceiver 910 a comprises circuitry operable to transmit andreceive cable television and/or DOCSIS signals via the cable 904. Datato be transmitted may be received via the backhaul link(s) 518, thetransceiver 514, and the mux/demux 912. Received data may be output ontothe link(s) 518 via the mux/demux 912 and transceiver 514.

The mux/demux 912 comprises circuitry operable to multiplex the signalsfrom the various transceivers 910 onto the link 518 and demultiplex datafrom the link(s) 518 to the various transceivers 910. In this manner,signals of a variety of networks using a variety of protocols/standardsand operating on a variety of frequencies (e.g., the Wi-Fi may operateon the 3.4 GHz band, the cellular may operate on one or more of the manylicensed bands used for cellular, and the cable network may operate onfrequencies from 50 MHz to 1 GHz) may be backhauled via one or moremicrowave backhaul links 518

Wi-Fi, cellular, and cable are merely examples of types of transceiverswhich may be integrated along with microwave backhaul transceiver 514.In general, any number and/or type of transceivers may be integratedwith the microwave backhaul transceiver 514 and backhauled via thelink(s) 518.

In accordance with an example implementation of this disclosure, amicrowave backhaul transceiver (e.g., 514 a) comprises a conditionsdetermination circuit (e.g., 530) operable to determine atmosphericattenuation between the microwave backhaul transceiver and a linkpartner (e.g., 514 b) with which the microwave backhaul transceivercommunicates over one or more microwave links (e.g., 518). Thetransceiver may comprise link control circuit (e.g., 532) operable tocontrol parameters of the one or more microwave links based on thedetermined atmospheric attenuation. The parameters of the one or moremicrowave links may comprise, for example, bandwidth (i.e., amount ofspectrum used for the links). The link control circuit may, dynamicallywhile the one or more microwave links is active, increase the bandwidthof the one or more microwave links in response to an increase in thedetermined atmospheric attenuation and decrease the bandwidth of the oneor more microwave links in response to a decrease in the atmosphericattenuation. The parameters of the one or more microwave links maycomprise how many of the one or more microwave links that are active.The link control circuit may, dynamically while the one or moremicrowave links is active, disable a secondary link of the one or moremicrowave links in response to the determined atmospheric attenuationfalling below a determined threshold and enable the secondary link ofthe one or more microwave links in response to the determinedatmospheric attenuation rising above the determined threshold. Theparameters may comprise a duty cycle of the one or more microwave links.The link control circuit may, dynamically while the one or moremicrowave links is active, decrease the duty cycle in response to adecrease in the determined atmospheric attenuation and increase the dutycycle in response to an increase in the determined atmosphericattenuation. The conditions determination circuit may communicate over anetwork (e.g., the Internet) with a weather service to obtain data(e.g., precipitation forecast, humidity forecast, smog forecast, etc.);and use the obtained data for the determination of the atmosphericattenuation. The link control circuit may, dynamically while the one ormore microwave links is active, decrease a transmit power used for theone or more microwave links in response to a decrease in the determinedatmospheric attenuation and increase the transmit power in response toan increase in the atmospheric attenuation.

Other embodiments of the invention may provide a non-transitory computerreadable medium and/or storage medium, and/or a non-transitory machinereadable medium and/or storage medium, having stored thereon, a machinecode and/or a computer program having at least one code sectionexecutable by a machine and/or a computer, thereby causing the machineand/or computer to perform the processes as described herein.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputing system, or in a distributed fashion where different elementsare spread across several interconnected computing systems. Any kind ofcomputing system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computing system with a program orother code that, when being loaded and executed, controls the computingsystem such that it carries out the methods described herein. Anothertypical implementation may comprise an application specific integratedcircuit or chip.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

What is claimed is:
 1. A system comprising: a receiver operable todetermine a performance metric of a microwave backhaul link; and a linkcontrol circuit operable to coordinate one or more signaling parametersused for the microwave backhaul link and one or more signalingparameters used for a mobile access link, based on the performancemetric.
 2. The system of claim 1, wherein the signaling parameters usedfor the microwave backhaul link comprise: a number of bits per sampleused for transmission of common public radio interface (CPRI) data overthe microwave backhaul link; and a code rate of the CPRI data.
 3. Thesystem of claim 1, wherein the determination of the performance metriccomprises a determination of signal-to-noise ratio of the microwavebackhaul link.
 4. The system of claim 1, wherein the performance metricof the microwave backhaul link comprises an error rate.
 5. The system ofclaim 1, wherein the performance determination circuit is operable todetermine an environmental condition.
 6. The system of claim 5, whereinthe environmental condition comprises an atmospheric attenuation.
 7. Thesystem of claim 6, wherein the atmospheric attenuation is determinedaccording to data communicated with a network.
 8. The system of claim 1,wherein the performance determination circuit comprises sensors formeasuring atmospheric conditions.
 9. The system of claim 1, wherein theperformance determination circuit is operable to predict futureatmospheric attenuation.
 10. The system of claim 1, wherein the linkcontrol circuit is operable to jointly control signaling parameters usedfor the microwave backhaul link and the mobile access link according toa current performance metric and a predicted performance metricdetermined by the performance determination circuit.
 11. A methodcomprising: determining a performance metric of a microwave backhaullink; and coordinating signaling parameters used for the microwavebackhaul link and signaling parameters used for a mobile access linkbased on the determined performance metric of the microwave backhaullink.
 12. The method of claim 11, wherein the signaling parameterscomprise: a number of bits per sample used for transmission of commonpublic radio interface (CPRI) data over the microwave backhaul link; anda code rate of the CPRI data.
 13. The method of claim 11, whereindetermining the performance metric comprises determining asignal-to-noise ratio of the microwave backhaul link.
 14. The method ofclaim 11, wherein the performance metric of the microwave backhaul linkcomprises an error rate.
 15. The method of claim 11, wherein determiningthe performance metric comprises determining an environmental condition.16. The method of claim 15, wherein the environmental conditioncomprises an atmospheric attenuation.
 17. The method of claim 16,wherein the atmospheric attenuation is determined according to datacommunicated with a network.
 18. The method of claim 11, whereindetermining the performance metric comprises measuring atmosphericconditions.
 19. The method of claim 11, wherein determining theperformance metric comprises predicting future atmospheric attenuation.20. The method of claim 11, wherein the method comprises jointlycontrolling signaling parameters used for the microwave backhaul linkand the mobile access link according to a current performance metric anda predicted performance metric.